Mega-tsunami hit southeast Asia 700 years ago

By Tan Ee Lyn

HONG KONG (Reuters) - A mega-tsunami struck southeast Asia 700 years ago rivalling the deadly one in 2004, two teams of geologists said after finding sedimentary evidence in coastal marshes.

Researchers in Thailand and Indonesia wrote in two articles in Nature magazine that the tsunami hit around 1400, long before historical records of earthquakes in the region began.

"Tsunamis are something we never experienced before and after 2004, people thought it was something we would never experience again," Kruawun Jankaew of Thailand's Chulalongkorn University told Reuters by telephone.

"But from this, we are able to identify that the place has been hit by a mega tsunami in the past. So even though it is infrequent for this part of the world, it still happens and there is a need to promote tsunami education for coastal peoples."

The 2004 tsunami left 230,000 people either dead or missing across Asia, from Sri Lanka and India to Thailand, the Maldives and Indonesia. More than 170,000 of these victims were in Aceh province in Indonesia.

Jankaew's team studied a grassy plain on Phra Thong, an island north of Phuket in Thailand, where the 2004 tsunami reached maximum wave heights of 20 metres above sea level.

A separate team led by Katrin Monecke from the University of Pittsburgh looked at the sedimentary records on coastal marshes in Aceh, where the waves reached 35 metres.

They explored low areas between beach ridges called "swales" -- which are known to trap tsunami sand between layers of peat and other organic matter -- and discovered a layer of sand beneath the most recent layer (2004), from 600 to 700 years ago.